1. Field of the Invention
The present invention relates to a printing plate automatic exposing device which places a printing plate at a predetermined position on a surface plate and exposes an image onto the printing plate.
2. Description of the Related Art
A technique (printing plate automatic exposing device) has been developed which, by using a printing plate (hereinafter, xe2x80x9cphotopolymer platexe2x80x9d) in which a photosensitive layer (e.g., a photopolymerizable layer) is provided on a support, an image is recorded directly by a laser beam onto the photopolymerizable layer of the photopolymer plate.
In this technique, in order to rapidly carry out image recording onto photopolymer plates, the photopolymer plates must be fed one after the other. A plurality of photopolymer plates are made to wait in a stacked state at a predetermined position, and are automatically removed one at a time, positioned on a surface plate, and fed into an exposure section.
Conventional devices are not provided with a means for detecting whether or not a photopolymer plate is placed on the surface plate. As a result, there is the possibility that proper processings, based on the results of detection as to whether there is or is not a photopolymer plate placed on the surface plate, will not be carried out. For example, there is the possibility that the process will proceed to the next step after the exposure step regardless of the fact that a photopolymer plate is not correctly placed on the surface plate. Further, for example, there is the possibility that, at times when the printing plate automatic exposing device is initially used or times when use of the printing plate automatic exposing device is started up again after the supply of electricity thereto has been stopped, a new printing plate will be conveyed regardless of the fact that a printing plate is placed on the surface plate, and thus two printing plates will be placed on the surface plate, leading to image defects.
In view of the aforementioned, an object of the present invention is to provide a printing plate automatic exposing device which detects whether or not a printing plate is placed on a surface plate, and which carries out appropriate processing on the basis of the results of detection.
A first aspect of the present invention is a printing plate automatic exposing device in which a printing plate supplied to a predetermined position on a surface plate is vacuum suction adhered onto the surface plate by air being sucked from a suction hole and a suction groove provided in the surface plate, and in this state, an image is exposed onto the printing plate, said printing plate automatic exposing device comprising: a detection portion provided independently from the suction hole and the suction groove at a position on the surface plate which is blocked by printing plates of all dimensions which are set on the surface plate; a suction device communicating with the detection portion and sucking in air from the detection hole; and a pressure sensor communicating with the detection portion, and able to detect that a degree of vacuum of the detection portion is a predetermined degree of vacuum which is set in correspondence with a case in which a printing plate is set on the surface plate.
The predetermined degree of vacuum is set on the basis of the capability of the suction device and on the air permeability (amount of leakage of air) between the suction hole and the printing plate.
Further, the pressure sensor of the printing plate automatic exposing device of the first aspect may be a pressure sensor which outputs a signal which is linear with respect to the degree of vacuum. Or, the pressure sensor may be a pressure switch which outputs a constant signal (a signal turning a contact on and off) when the degree of vacuum is greater than or equal to a set degree of vacuum.
In the printing plate automatic exposing device of the first aspect, the printing plate is supplied to a predetermined position on the surface plate. By sucking air from the suction hole provided in the surface plate, the printing plate can be vacuum suction adhered to the surface plate, and an image can be exposed onto the printing plate in this state.
Further, in the printing plate automatic exposing device, the detection hole is provided in the surface plate independently of the suction hole and the suction groove for vacuum suction adhesion. The detection hole communicates with the suction device and the pressure sensor. When the printing plate is supplied onto the surface plate, in order to detect whether the printing plate is placed on the surface plate, the suction device sucks air from the detection hole, and the pressure sensor detects the degree of vacuum of the detection hole.
Here, when a printing plate is set on the surface plate, i.e., when the detection hole is blocked by the printing plate, the degree of vacuum of the detection hole is the predetermined degree of vacuum. At this time, the pressure sensor detects that the degree of vacuum of the detection hole is the predetermined degree of vacuum, and outputs a predetermined signal.
On the other hand, when no printing plate is set on the surface plate, i.e., when the detection hole is not blocked by the printing plate, the degree of vacuum of the detection hole is not higher than the predetermined degree of vacuum. As a result, the pressure sensor does not detect that the degree of vacuum of the detection hole is the predetermined degree of vacuum, and does not output the predetermined signal.
In this way, in the printing plate automatic exposing device of the first aspect, on the basis of the output signal of the pressure sensor, it can be detected whether or not a printing plate is placed on the surface plate. In this way, a printing plate automatic exposing device which carries out appropriate processing on the basis of the detection signal of the pressure sensor can be obtained.
Moreover, because an inexpensive pressure sensor is used, the printing plate automatic exposing device can be provided at a low cost.
A second aspect of the present invention is a device for automatic exposure of printing plates in accordance with image data, the device comprising: (a) a surface plate mountable in the automatic exposure device for receiving printing plates thereon, the surface plate having a suction hole, a suction groove and a detection hole; (b) a suction system in fluid communication with the suction hole and groove and the detection hole, and operable for applying reduced pressure thereto for suction adherence of printing plates and for use in printing plate detection; (c) a pressure sensor in fluid communication with the detection hole, and providing an output signal when the degree of vacuum in the detection hole at least equals a level corresponding to when a printing plate is received on the surface plate obstructing the detection hole with reduced pressure applied to the detection hole by the suction system; (d) a scanner operable for exposing a printing plate in accordance with image data; and (e) a controller connected in electronic communication to the scanner and the pressure sensor and receiving the output signal and controlling the scanner, the controller controlling processing based at least in part, in accordance with the signal received.
A third aspect of the present invention is a method for detecting printing plate presence on a support surface in an exposure device, the method comprising the steps of: (a) providing a hole on the support surface; (b) applying a reduced pressure to the hole; (c) sensing the pressure in the hole using a pressure sensor; and (d) determining that a printing plate is present on the support surface if the degree of vacuum sensed is at least equal to a predetermined level, and otherwise determining that a printing plate is not present on the support surface.